This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Jeffrey Dahmer. Richard Kuklinski. Charles Manson. Kenneth Bianchi. Dennis Rader. Bernie Madoff. These are a few of the most infamous psychopaths of the past 50 years.

While many people who fit the profile of a psychopath aren't serial killers or notorious criminals, they share a number of the same characteristics. And that can make them nightmares in the workplace.

"What's fundamentally different about [psychopaths] is that they do not have a conscience regarding their conduct, no matter how catastrophic the consequences might be," explained Kelly Wilson, president and director of forensic services for Edina, Minn.-based PsyBar LLC, during a presentation at the 2013 National Safety Congress and Expo in Chicago.

"Many of them are literally unable to experience human attachment or genuine human emotion."

Even if their behavior isn't criminal, psychopaths bring a number of toxic traits into the workplace, Wilson explained. Citing the research of the late Hervey Cleckley – a pioneer in the study of psychopathy – Wilson noted that psychopaths tend to be:

Superficially charming and gregarious.

Inhumanly calm.

Unreliable.

Dishonest and insincere.

Antisocial.

Arrogant and egocentric.

Unresponsive to interpersonal relations.

Outrageous and uninviting in their behavior.

Psychopaths, Wilson noted, also tend to have "an inclination for breaking rules and pushing the limits of acceptable behavior" – which can undermine workplace-safety efforts in a heartbeat.

In addition to these and other common characteristics, psychopaths often share a chameleon-like ability to blend into normal society without being noticed (a concept introduced in Cleckley's landmark book "The Mask of Sanity").

"Psychopaths just have a stillness about them, where you don't really know what's going on," Wilson said. "It's called the mask of sanity – where they put on their everyday face, but what's behind it is something altogether different."

Psychopaths in the Workplace

If psychopathy seems like the stuff of "truTV," consider this: Experts estimate that one in 100 men and one in 300 women in the United States are psychopaths.

Robert Hare, author of "Snakes in Suits: When Psychopaths Go to Work," estimates that there are 2 million psychopaths in the United States, while others put that number closer to 3 million, Wilson said.

The bottom line: Psychopaths likely are lurking in your workplace, even if their behavior isn't as extreme as that of the notorious criminals listed at the beginning of the story.

"They are out there, and they're built the same," Wilson said.

Psychopaths can be executives, managers or supervisors, but they just as easily can be front-line employees or co-workers.

Workplace psychopaths might be very likeable – almost too likeable. But underneath the affable facade, they often take great pleasure in undermining others, taking credit for co-workers' accomplishments and fomenting conflict and confusion.

Likewise, they can engage in character assassination, blackmail and seduction (Wilson pointed to the sexual predator portrayed by Jennifer Aniston in the movie "Horrible Bosses") and a pattern of manipulative, unethical conduct.

And when their behavior gets them in trouble, workplace psychopaths are well-equipped – seemingly – to defend themselves.

"They always have a ready response if they get confronted at work," Wilson explained. "Where 'this is your final warning and you're going to get fired,' they will always have five reasons why it happened without batting an eye. It's always a quick response."

Often, they leverage their superficial charm to somehow turn the tables on their superiors.

"You find when they walk out of a meeting that they actually never admitted or acknowledged any wrongdoing, but you still felt that you kind of liked them," Wilson said. "It's this likeability factor and sucking you in and making you question yourself that's pretty common with these folks."

Beware of First-Impression Bias

The best way to keep psychopaths out of the workplace is to avoid hiring them in the first place, Wilson said.

"That's not always an easy thing to do, because they can be very likeable," she added.

It's even harder because of human nature. We make first impressions quickly, and once those impressions are cemented, we're resistant to altering those impressions later (a concept called "first-impression bias").

Whether consciously or subconsciously, psychopaths seem to take advantage of this.

"Their secret goal is to make themselves look good with as little real accomplishment as possible," Wilson said. "They tend to hide this very well in the beginning. They act like they're working hard, but they're really doing whatever they can to skirt any kind of work."

Wilson's advice to employers: Do your due diligence.

Because of their bad behavior, psychopaths often bounce from job to job, targeting employers with lax screening procedures. To vet them, she recommends conducting criminal-background checks and credit checks, and asking for pay slips from prior jobs to verify the dates on their applications.

Also, when contacting references, consider calling the main switchboard of the reference's employer instead of the number listed on the applicant's resume.

"Many people will put cellphone numbers of their friends and call them 'Mr. So and So,'" Wilson explained. "We recommend that people find out what the company building is, call the brick-and-mortar establishment and try to find the supposed boss that way."

Other telltale signs to look for in an interview include:

Ordinary achievements described as monumental.

Appearing too relaxed.

Inconsistencies with the resume.

An inability to describe the personal qualities of former supervisors or co-workers.

"It's always a good idea to ask them for details about things," Wilson said. "Ask them to name a mistake they made. That's really hard for a psychopath, other than getting caught.

"But then ask them how it impacted others. Whenever it has something to do with the feelings of others, they don't have the words to describe that very well."